Transfer device for cassettes containing radioactive samples in a gamma counter and cassette system

ABSTRACT

A transfer device for cassettes containing radioactive samples and a cassette system in a gamma counter provided with a well-type detector. The transfer device comprises a path (61), by which cassettes (11, 12, 13) can be moved one at a time to a lifting position where sample containers can be lifted and moved to the measuring unit (50) for measuring. At the lifting position a vertical long side of the cassette (11, 12, 13) is locked in place against a vertical surface or edge (63) of the table (61) so that the distance between the center of the sample container (17) in the cassette from the vertical surface or edge of the table is substantially directly proportional to the radius of the sample container. The cassette system comprises at least two different cassettes (11, 12, 13) which are of the same length but which can take a different number of adjacently placed sample containers (17 ) of different sizes. The sample containers in each cassette are the same size. The width of the cassette is directly proportional to the width of the sample containers placed therein. The cassettes are also symmetrical about their longitudinal axis so that the center line of the sample containers is coincident with the center line of the cassette. The two long sides of each cassette are nearly similar and vertical.

BACKGROUND OF THE INVENTION

The invention relates to a transfer device for cassettes containingradioactive samples in a gamma counter provided with at least onewell-type detector, the transfer device for the cassettes comprising atransfer unit or a path, which is a table provided with at least oneconveyor, by which the cassettes of different widths, containing samplecontainers of different sizes, can be moved one at a time to a liftingposition wherefrom the sample containers can be lifted into themeasuring unit for measuring.

Gamma counter measurements of radioactive samples are commonly conductedusing either RIA (Radio Immuno Assay) devices, then the question usuallybeing of a mass survey, or research devices, the question being of asingle research of a small series only. RIA devices must be fast andtherefore they handle several samples simultaneously. A research deviceneed not be so fast and samples may, instead, be in containers orcassettes of different sizes. The radioactive isotope of the samples mayalso emit high energy radiation and therefore the detector of a researchdevice must be larger and the lead shield must be much better than in aRIA device.

Either well-type or diametrically through hole-type detectors aregenerally used in counters. Well-type detectors are provided with ahollow, formed in the detector material, in which the sample isinserted. In hole-type detectors a hole goes through the detectormaterial into which the sample is lifted. A well-type detector is easierto manufacture. It also has better efficiency and it is easier to shieldthan a hole-type detector.

Known gamma counters have been disclosed, e.g., in the U.S. Pat. No.4,029,961 and 4,035,642. In these devices the sample containers to bemeasured have been placed in cassettes of ten containers and themeasuring device takes one cassette at a time for measuring. As thereare ten gamma detectors in the device, all samples in the cassette canbe measured simultaneously. However, this kind of device is onlysuitable for use in RIA measurements because it would become too largeand expensive for use in research if manufactured using known technique.Moreover, one cannot use a well-type detector in this kind of devicebecause the sample is lifted into the detector.

For economical reasons research devices have only one large andwell-shielded detector. Since it has not been possible to combine RIAdevices and research devices, those isotope laboratories which want todo both RIA counting and actual gamma research have been forced topurchase two separate counters. Therefore, for economical reasons,counters are also manufactured with 1, 2, or 4 detectors. They arelarger and better shielded than necessary in actual RIA work andtherefore they can, to a certain extent, be also used in research work.However, the drawback in RIA work is lower speed compared to actual RIAdevices and limited efficiency in research work. Furthermore, the volumeof samples cannot exceed that of RIA samples.

SUMMARY OF THE INVENTION

The object of this invention is to provide a new transfer device forcassettes, being of different sizes and containing radioactive samples.The invention is characterized in that, at the lifting position, onevertical long side of the cassette is locked in place against the edgeof the table so that the distance of the center of the sample containerin the cassette from the edge of the table is principally directlyproportional to the radius of the sample container.

The object of the invention is also a cassette system for use in thetransfer device presented above. The cassette system comprises at leasttwo different cassettes, being of the same length but differing fromeach other principally in that cassettes can take a different number ofadjacent sample containers depending on their size, the samplecontainers in the same cassette being of the same size with each other.

The invention is characterized in that the width of the cassette isprincipally directly proportional to the width of the sample containersto be placed therein, that the cassettes are principally symmetricalabout their longitudinal axis so that the center line of the samplecontainers is principally coincident with the center line of thecassette, and that both the long sides of cassette are principallysimilar and vertical.

The other characteristics of the invention have been set forth in theensuing claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following by means of exampleswith reference to the accompanying drawings in which

FIG. 1 shows an axonometric view of a gamma counter according to theinvention.

FIG. 2 shows the gamma counter of FIG. 1 viewed from the side.

FIG. 3 corresponds to FIG. 2 and shows the gamma counter moving a samplecontainer into the measuring unit.

FIG. 4 shows a sectional view taken along the line A--A in FIG. 2.

FIG. 5 shows sample container cassettes, being movable on the transfertable, of the gamma counter of FIG. 4.

FIG. 6 shows the sample cassette, viewed from the end, at a positionwhere the samples are being lifted into the measuring unit.

FIG. 7 shows the end of the sample cassette of FIG. 6 viewed from theside.

FIG. 8 corresponds to FIG. 6 and shows another embodiment of the samplecassette.

FIG. 9 shows the end part of the sample cassette of FIG. 8 viewed fromthe side.

FIG. 10 corresponds to FIG. 6 and shows a third embodiment of the samplecassette.

FIG. 11 shows the end of the sample cassette of FIG. 10 viewed from theside.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an axonometric view of a gamma counter according to theinvention, the principal functional parts being a measuring unit 50 anda lifting device 40 consisting of a transfer device unit 30 and a gripunit 20, belonging thereto, for the sample container holders. Thetransfer device unit 30 is mounted on a cantilever beam 41 which can bemoved in vertical direction in order to lift a sample container holderout of the sample container cassette and to lower it into the measuringunit 50.

The grip unit consists of a slide 31 moving on a horizontal guide bar42, the slide having three pairs of grip nails 24 attached thereto.These form the three grip elements 21, 22, and 23, being of differentsizes, for gripping the holders, being of different widths, of samplecontainers.

The measuring chamber of the measuring unit 50 is provided with only asingle big hole 53 for the detector. The gamma counter in FIG. 1 is,therefore, meant for use in research and it can take sample containersof different sizes in cassettes of different sizes one at a time foranalysis.

Operation of the device of FIG. 1 is described in greater detail in thefollowing figures.

FIG. 2 shows the main parts of the gamma counter of FIG. 1 viewed fromthe side. Sample container cassettes 11, which contain sample containerholders 15 and, inside them, sample containers 17, are placed in thecassette transfer unit 60 on the measuring table 61, being in connectionwith a conveyor 62 which moves one cassette at a time to a position forlifting the sample containers. In FIG. 3 its location is in the leftcorner of the measuring table 61, the cassette 11 being shown as across-sectional view. In this gamma counter one can use samplecontainers and their cassettes of three different sizes because the gripunit 20 has three grip elements 21, 22, and 23 of different sizes.

The lifting device 40 accomplishes the transfer of samples to themeasuring unit 50 for measuring. The transfer unit 30 is moved on ahorizontal guide bar 42 of the cantilever beam 41 by means of a coggedbelt 47 and an electric motor 46. Based on information obtained from acassette identifier, located on the cassette path before the measuringpoint, the slide 31 in the transfer unit 30 moves so that a grip elementof the right size is right above the cassette. It can be seen in thefigure that the smallest of the grip elements 21, 22, and 23 has beenselected i.e. the one with the reference number 21. The grip nails 24will subsequently lift the sample container holder 15 out of thecassette 11. The vertical movement has been arranged so that the wholecantilever beam 41 rises with a block 49 slidably mounted on the guidebars 48.

FIG. 3 illustrates a situation where the transfer unit 30 of the gammacounter has moved the holder 15 of the sample container in a horizontaldirection right above the measuring hole 53 of the measuring unit 50.After this the cantilever beam 41 on the whole is lowered, the samplecontainer going down into the measuring hollow 53 having a well-typedetector 55. The measuring unit 50 has such a construction that themeasuring chamber 51, being made of lead, is provided with a hollow ofthe same size as the detector 55.

The detector has been installed by lowering it downward from above intoits hollow and mounting a protective ring 57 on top. The advantage ofthe construction is that, whenever necessary, one can easily change thedetector from above.

FIG. 4 shows the gamma counter of FIG. 1 viewed from above. In thefigure the measuring table 61, having the measuring unit 50 in themiddle, forms the cassette transfer unit 60. The measuring unit has ameasuring chamber 51 containing one detector. Sample container cassettes11, 12, and 13 of different widths are placed on the table 61 where theyare transferred in turn for measuring by means of conveyors 62. Thecassettes rotate along a path round the measuring unit 50. A transducer65 for identifying cassettes has been placed on the path, before themeasuring point, the transducer identifying the width of the cassetteand the size of the sample containers therein and controlling that asuitably sized grip element is transferred above the sample. This deviceis suitable for research work where simultaneous measurement of manysamples is generally not required, but the detector is large enough andthe walls of the measuring chamber are thick enough.

FIG. 5 shows three sample container cassettes 11, 12, and 13 ofdifferent sizes. Their lengths are the same but the widths aredifferent. The width of the cassette defines the size of samplecontainers it can take. The narrowest cassette 11 can take ten smallsample containers along with their holders. The cassette is thenprovided with the corresponding number of recesses for the samplecontainers. A medium wide cassette takes eight medium-sized samplecontainers and the widest cassette takes five wide sample containers.The gamma counter shown in FIG. 1 can measure all sample container sizesmentioned above. To identify cassettes of different sizes the end partsof all cassettes have been provided with identification parts 1 and 2.The transducer, placed in connection with the transfer unit, identifiesthe width of the cassette by the form of the identification part.

The sample container cassette 11 is schematically shown in FIG. 6 on themeasuring table 61 of the transfer unit 60 at a position where thesamples are lifted up. It is seen in the figure that there is a guide64, raising from the surface of the table, formed along the path on thetable. A corresponding recess has been formed on the cassette 11 sothat, on the lower edge of the cassette, a guide edge 18 is formed, thewidth corresponding to the distance between the guide 64 on the tableand the edge 63 of the table. When the guide edge 18 of the cassettemoves in the groove between the guide and the table edge, the cassettestays sideways firmly in place with its other side leaning against theedge 63 of the measuring table. The forward transfer movement of thecassette is performed so that the nail of the pulling device inside thetable edge 63 grips the opening 14 on the side wall of the cassette. Atthe same time, this nail of the pulling device in the opening of thecassette prevents the cassette from rising, the cassette being heldfirmly on the path 61 also in the vertical direction.

FIG. 7 shows as a side view that end of the cassette which comes firstto the place where the samples are to be lifted. As shown in the figure,the cassette is provided with two identification parts 1 and 2 by meansof which the transducer 65 shown in FIG. 4 identifies the width of thecassette. In this cassette both parts are closed and so the transducer,identifies the cassette to be a thin type. FIG. 7 also shows the hole 14for the nail of the pulling device locating on the side of the cassette.

FIG. 8 shows a medium wide cassette 12. It is shown in the figure thatthe guide 64 on table 61 and the nail of the pulling device lock alsothis cassette firmly in place on the path. This is due to the fact thatthe guiding edge 18, in the lower edge of the cassette, is quite similarto that of a thin cassette, apart from the fact, that the recess underthe cassette is wider which is due to the greater width of the cassette.So, one can reliably move cassettes of different widths on the transferpath as long as the width of the guiding edge 18 in their lower edgecorresponds to the distance of the guide 64 of the table and the edge 63of the table from each other.

FIG. 9 shows also that a medium wide cassette 12 has been marked for theidentification transducer in such a way that only the upperidentification part 1 is closed.

FIG. 10 shows a wide cassette 13 whose control is performed exactly inthe same way as that of the other cassettes. Only the identificationparts are different, as seen in FIG. 11. In this case only the loweridentification part 2 is closed.

It can be seen in FIGS. 6, 8 and 10 that the other side of the cassettes11, 12, and 13 leans against the same edge 63 of the measuring table 61so that the middle part of a wider sample cassette remains farther awayfrom the edge than that of a narrow cassette. This distance of themiddle part from the edge 63 is marked with letters a, b, and c in thefigures.

Since the distance of the middle part of the cassette, i.e., a,b, and cvaries, the cassette transfer unit in a gamma counter of FIGS. 1 and 2has been designed to operate so that the slide on the horizontal guidebar is controlled by the information obtained from the identificationtransducer. Firstly, the right grip element is chosen out of the gripunits 21, 22, and 23 shown in FIG. 2. After that, the middle part of thechosen grip element is moved to a distance a, b, or c from the edge 63.Now, the cassette can be moved so that the holder of the samplecontainer moves between the nails 24 of the grip element 21 and thelifting of the sample can start thereafter.

It is obvious to a specialist that the different embodiments of theinvention can vary within the scope of the ensuing claims.

We claim:
 1. A transfer device for transferring cassettes of differentwidths which contain radioactive sample containers of different sizes ina gamma counter, comprising:a plurality of cassettes of different widthswhich contain sample containers of correspondingly different sizes, ameasuring unit having at least one well-type detector, a transfer unithaving at least one conveyor for moving one of said cassettes ofdifferent widths to a lifting position where a sample container islifted from said one cassette and moved for insertion into saidwell-type detector, means forming a vertical surface adjacent saidlifting position, and means on and adapted to cooperate between each ofsaid cassettes of different widths and said transfer unit for locking avertical long surface of said cassette against said vertical surface,whereby the distance between said vertical surface and the center ofeach sample container in a cassette to be locked against said verticalsurface is substantially directly proportional to the radius of thesample containers contained in said cassette to be locked against saidvertical surface.
 2. A transfer device for transferring cassettescontaining radioactive containing sample containers of different sizesin a gamma counter of the type including a measuring unit having atleast one well-type detector, a transfer unit having at least oneconveyor for moving a cassette to a lifting position where a samplecontainer is lifted from said cassette and moved for insertion into saidwell-type detector, wherein the improvement comprises:means forming avertical surface adjacent said sample container lifting position, and acassette system comprising a plurality of cassettes having two verticalsides of substantially the same length with each cassette adapted toreceive a number of adjacently placed sample containers of the same sizeand at least one of said cassettes having a width different from thewidth of other ones of said cassettes so as to receive a number ofsample containers having a width different from the width of samplecontainers in said other ones of said cassettes, said width of each ofsaid cassettes being substantially directly proportional to the width ofthe sample containers in each respective cassette, each of said cassettebeing substantially symmetrical about a longitudinal center line with acenter line of the sample containers received therein substantiallycoincident with the longitudinal center line of each cassette, and meanson and cooperating between each cassette and said transfer unit forlocking one of said vertical sides of each cassette against saidvertical surface adjacent said sample container lifting position.